Drying apparatus with air desiccating means and automatic regenerating means therefor



Nv. l1.2, 1946. R. v. HEusER 2,411,039

' BRYING APPARATUS` WITH AIR DESICCATING MEANS ND AUTOMATIC REGENERATING MEANS THEREFOR INVENTOR 41,1%/ u. #fz/sri,

A'rroRNEY Nov. l2, 1946. R. v. Hl-:usER 2,431,039

DRYING APPARATUS WITH AIR DESICCATING MEANS AND AUTOMATIC REGENEHATING MEANS THEREFOR l Filed Oct. 12, 1943 4 Sheets-Sheet 2 ATI' NEY y Nov. l2, 1946. R. v.-HEUsER DRYING ARPARATUS WITH AIR DESICCATING MEANS AND AUTOMATIC REGENERATING MEANS THEREFOR mvENToR fag/2H ,eff-asf?,

4 Sheets-Sheet 3 Filed oct. 12. 1943 Nov. EZ, w45. v. HEUsER DRYING APPARATUS WITH AR DESICCATING MEANS AND AUTOMATIC REGENERATING MEANS THEREFOR Filed OCL. 12, 1943 4 Sheets-Sheet 4 INVENTOR P41/9H V. Wfl/55A,

Patented Nov. 12, 1.946

UNITE 'rais Ralph V. Heuser, WeavervillavN. C.

1 claims.

The present invention relates to apparatus for drying and desiccating materials with the aid of v of relative humidity.

In homes the apparatus wil1 be useful 'for storing and preserving various food products such as crackers, cookies, cereals, etc., once their con-` tain'er hasbeen opened, Vin a crisp and fresh condition, hence preventing the same from becoming soggy and unpalatable. It will also prevent the caking of powdered and granulated products such Furthermore it as sugar, flour, salt and spices. will overcome certain diiliculties connected with the dehydration of vegetables in ovens bythe hotairdrying process. Some of the dried vegetables are very hygroscopic, hence in order to prevent them from reabsorbing moisture and becomeincals would be eliminated. Besides a more rapid drying would be had as compared with desiccators operating at maximum efficiency only when freshly charged.

In hospitals and first-aid stations the apparatus would beadvantageous for storing and maintaining sterilized dressings, sutures, bandages as well as surgical instruments, Petridishes, etc., in an aseptic' condition after sterilization, since very dry hair has a strongly inhibitory leffect, on the growth and propagation of bacteria' and other dangerous organisms.

The few aforementioned uses are merely illustrative of numerous applications in which an inexpensive, reliable drying apparatus is needed.` One of the principal objects of the inventionis,l

therefore, `to provide an inexpensive, reliable andl elcient apparatus for drying and desiccatingmaterials in the vabove' `mentioned relationships.

Other objectsV of the invention will be apparent from the following description thereof. l

Application october 12, 1943, serial'No. 505,931

be lubricated and it operateswithoutany attention. It is an improvement over the drying device described in my U. S. Patent 2,067,920 which is .non-automatic inoperationand requires a persons attention in several manipulations.

The present invention is based in part on the followingl principle: Bodiesof adsorbent composition, preferably in the` form of a molded plate (or a multiplicity of plates), take up the moisture liberated from the materials to be dried. The, resultant gain in weight by the plate is instrumental in causing an electric circuit to be closed by a sensitive electricswitch, the ensuing electric 4 current passing-through a system of resistance wires embedded within ,the plate or in close proximity thereof for purposes ofremoving the adsorbed .water from the plate. When this is the case a bimetallic strip opens the electrics'witch, the plate cools down and -is again in condition to adsor-b nioisture. The plate fulfills, therefore, the kdual role of functioning as an adsorbing lmedium and as an. organ of the control ymechanism of which it forms a part. This mechanismis produced in the form of a balance, the plate being counterpoised by a' movable weight, by a cantilever spring o r by a helical spring.

From' the above it is seen that the apparatus works in a cyclic manner. The onset of the desorbing phase is made adjustable by changing the moment created by the counterpoise. This is done by changing either the distance of the weight from the fulcrurn, or by changing the leverage of the cantilever spring or the stiiness of the helical spring. Furthermore provision is also made for regulating the period during which the electric current is caused to ow through the heating system. 1

y The invention will be more readily understood by reference to the accompanying drawings, `in

40 which like reference characters indicate'like parts.

In ythese drawings Fig. 1 is a vertical cross sectional view taken alongthe line I-I of Fig. 2, n y

Fig. 2 is a vertical transverse section taken along 45fthe line 2.-2 of Fig.' l,

Fig. 3\ is a cross sectional underside view taken along the line 3-3 of Fig. 2 l 1 Fig. 4 is a perspective view of the plate and accessory parts shown inv Fig. 1, 2, 3," 4 50 Fig, Fig. `6 and Fig. 7 depict I three positions of the link mechanism at different stages of the `*drying operation,

Fig. 8 is a longitudinal view of an adsorbant plate A'with gravitational control mechanism, 55 Fig. 9 is a perspective view of the lever shown yinli'g.8, v f

Fig. 10 is a front'eleva'tion vand Fig. 11 va plan L view of four depending plates coupled together and a control mechanism based on the use ofk a 6c helical spring.

. y 3 .The apparatus according to lthis invention consists essentially, as shown in Fig. 1 of a container I subdivided .into two compartments 3 and 4 by' a horizontal partition 2. The lower compartment 3 servesasv a receptacle for the materials to 'bedried, and these may be introduced and withdrawn through a hinged door 5, around the rim of which is iitted a resilient gasket 6. Doory 5 also`-is provided with a bolt and latch (not shown in the drawing) permitting the door to be closed u tightly. Partition 2 is designed as a narrow shelf within the container I to accommodate a twowingedvdoor 1 capable of being tilted about pivots 8 in one direction only, as clearly indicated in the drawings. 'I'he top of the container I is provided with a similar door 9 which, for the sake of brevity will hereinafter be designated as upper' door as distinguished from door 1 hereinafter referred to as'v lower door. Upper door 9' is tiltable onl `pivots` I0 but `only in thel direction opposite to for the sudden closing of the lower door 1 as s oon v as the upper door 9 has begun to open by the action of a mechanism which will be described later.A The titling movement of the lower doorv 1 yis made dependent upon the movement of the upper door 9 through the intermediary of a link IJ and a pawl I3. The link II consists of tWo narrow strips of metal, and it is fastened to the underside of the upper door 9 and I2 in a freeswinging manner. The pawl I3 is suspended from the lower extremity of link I I and it swings freely on pivot I4. At certain periods of the cycle the pawl I3 engags the latch I5 which is rigidly attached to the rupperside of the lower door 1. At another stage. of the operation pawl I3 will be seized through the intermediary of the projecting finger by' a` hook I1 support n a free-swinging mannerat'point Iscr the bracket I9.

Duringthe absorbingstage vof the plate .the upper door 9 is closed and the lower door 1 remains ,cpen'w'hereby the air is enabled to circulate -fr'eely between the two compartments 3 and 4, as 'illustrated in Fig. 5. When subsequently Ithe upper door begins to open, as shown in Fig. 6, the linger I has been seized by the hook I1 therebyfcausin .the curved end of pawl I3 to free itself i'rom latch l I5 and causing the lower door 1 to suddenly fall shut in which position 4 y' 20 in a fixed position and thus insure the partial weight of the plate to exert its action on the spring 25 always at the same point once the proper adjustment has meen made. For this purpose the cups 23 secured'to angle 24 can be moved in the axis of the plate towards or away from the fiat spring 25, by/ causing the angle 24 to slide on brackets 2,6/in and out upon turning the screws 21 which are provided with locknuts 28. 'I'he plate is supported at the opposite end of its length by the blade 25, of suitable resiliency, via a curved metal strip 29 secured centrally to the underside of plate 20. to a base fixed on the wall I, of the container.

The spring 251s attached at its other end On the said base is also fastened the bracket 30. When'the spring blade 25 is mounted on the base it has sufficient upward tilt that it will assume a g proach the iron armature inside a Mercoid switch substantially horizontal position 'upon being 'g weighted down by the plate 20 after installation of the same. The distance of the center of the plate 20 from cups 23 advantageously is greater than the distance to where the strip 29 touches the spring 25,

As shown in Fig'. 2, the bracket 30 supports one end of a light shafting 3l on which is'secured bell crank 32. One armfof bell crank 32 touches the underside of blade 25 while the other arm bears a setscrew 33, .positioned opposite a bimetallic strip 34. To shaft 3| is also rigidly secured an arm 35 bearing a small permanent horse-shoe magnet 36. The slight downward deilection of the spring'25 (brought about by moisture adsorption of plate 20) causes the magnet to ap- 31, mounted on the angle 38.

Another,Y somewhat sturdier bimetallic strip 38, fastened to bracket 40, surmounts the plate 2li in a longitudinal direction. In its middle section it then resides during the entire desorption stage of the plate. As. the upper door 9 opens wider at this time link I I and pawl I3 will descend lower,

iinally slipping over the top of latch I5 and rel engaging it-on its underside, lso that when the upper door begins to close it will carry with it the lower door 1 and open it gradually. During itsupward travel the finger I6 of pawl I3 will clear .the hook I1 by pushing it slightly ,toward the-.wall of the container. `The hook I1 is then again in positiongto trip the pawl I3 when the'subsequent opening'of the upper door loccurs. .v

compartment 4 also houses the .adsorbent plate' 20 in the interior 4of which is embedded agstretched coilof electric resistance wire 2|. At one end of its` length plate 20 is supported on two prongs 22, Fig. 2, by smallI cups 23 of glass or -metal., vWhile the prongs 22 are free to move 'strip 30 bears a heating element 4I consisting of 6 to 10 tunis of resistance wire wound around a thin asbestos bobbin, the wiring also being insulated -by asbestos or glass iiber fabric on the outside in such a manner as not to interfere with the curling motion4 of .the bimetallic strip under the influence of heat from the two sources. Through a perforation near thefree end of the strip 39 a metal rod 43 projects a short distance while its club shaped enlargement 42 rests on top of the strip. The other end of rod 43 passes through agidef and at the extreme end of rod 43 a cupy 45 is attached which holds a polished steel ball. The latter bears against a wing of the upper door 3, causing the ylatter to be opened when the electric current passes throughthe element 4I and the plate 20. A counter-weight 46, fastened to the inside of one of the'wings of door 9, serves as a means to insure the spontaneous closing of the door 9, when the rod43 retreats to its normal position related to the adsorbing stage of plate20. Counter-weight .46 isV air readily to escape into the open when the door 8 has opened. The electric currententers the apparatus through socket l49, the circuit wiring Fig. 3 and Fig. 4. In the present instance, however, a metal disc 50 secured to the underside of plate 20 rests on the tip 5I of an upwardly lever arm. The pin 52 supports also in a free rocking manner a spider with amis 51, `58 and 59. (Said spider is shown in the drawing infront of the lever.) An oset-finger 56 of the short lever arm projects over the top of arm 51 and causes. the latter to be turned downward when the weight of plate 20 increases due to moisture adsorption. In consequence of this the small horse-shoe magnet 36 attached to the arm 58 of the spider will approach the mercury switch 31, secured to bracket 53, until the magnetic attraction of the soft iron armature inside the switch 31 is sufficiently strong to seize and hold the magnet. The heat radiated from the underside of the plate 20 upon the bimetallic strip 34 causes the latter to curve downward until it touches the setscrew on the arm 58 and `turns lthe spider backward so that the magnet 36 becomes detached from the switch 31 which interrupts the electric current. At this Y juncture the lever as well as the spider are again at their original position. v

The drawings Fig. 10 and Fig. l1 illustrate a third embodiment of the present invention. Four ment 66 is usedfto support the middle part of thel frame by the intermediary of a helical spring on the pivots of two bell-crank levers 1 -The helical spring consists of the two parts' 61 and 68. By turning a knurleddisc 69 on the outside of container I and therefore` also by turning the threaded shaft 1| in one direction or other, the

two springs 61'and 68 can be tightened or re-' laxed at will without disturbing the position of attachment 66 and other parts of the control mechanism.

. this radiation being very small at rst.

and. is, therefore, the'preferred means to serve as an essential part of the construction of the 1fllirying apparatus according to the present inven- When the apparatus is put in operation and the electric current is beginning to flow through the resistance wire in the plate and heating element 4 I the bimetallic strip 39 will curl upward, thereby pushing the steel ball on top of rod 43 against one wing of the upper door 9 and causing the latter to be opened gradually. The heating element 4I is used for the purpose to cause the upper door 9 to be opened more promptly than would be the case if the bimetallic strip 39 received only the heat supplied through radiation from plate 20, y When door 8 has opened slightly the mechanism already previously described comes into play which causes Soon the lower door 1 to fall shut suddenly. afterward watervapor will be evolved from the plate ln increasing volume as the plate gets hotter. However the heat required for the evapora- 'tionof the water tends to check a rapid rise of side of the partiallyopened door. The action of air as a 'diluent prevents the water vapor from condensing on the cold walls and other surfaces of the upper compartment. An effective air circulation is set up by the' influx of cold air over the top of the downwardly inclined wing of door 9 into the interior. The inflow and outflow of the air is therefore in counter-current motion, and as a `resultof the rapidwithdrawal of heat by the 45 eliluent vapor mixture the drying chamber 3 re- When thus making the sensitivity to deformation of the helical spring adjustable by changing its stiffness (i. e. the tension under which it operates) itis obvious that a given weight incrementl acquired by the plate system 20a, 23h, 20c and 20d'as a result of water adsorption, can be caused to either-advance orretardthe closing of theelectric circuit and hence the onset of' the adsorbing phase.

Rod 65 is steadied in its upright position by being `linked at its lower end by a pin'12 to a lever 13 capable of swinging on pin 14 which is firmly secured to a bracket `15. A sleeve 16 on pin 12 Needless to say a. flat coil spring could also be used to operatefundera tension, varied at will for purposes of regulating the performance of the apparatus. However the previously described use of the double helicalspring simplifies the design mains cool and thewalls of the upper compartment 4 become only slightly warm.

When'the electric current is automatically interrupted by the removal of the small horse-shoe magnet from the Mercoid switch 31 the-air circulation is maintained for some time longer, while the plate 20 is cooling. Because of the fact that the return of the door 9 to its closed position procee'ds -in thermostatic relationship with Vthe rate of cooling of the plate 20, obviously the door 9 vcan never be in its closed position so long as the plate is still warm. This is important inasmuch as this circumstance insures that the plate 20 recovers its adsorptive potency as rapidly as possible. The same conditions prevail when a plu- 5 balancing mechanism.

rality of plates is employed, 'as shown in Fig. 1l, instead of a single plate. Alternatively it is not necessary that the en- 'tire number of plates be used together in the Instead, only one plate, but of the same size as the others may function as a pilot plate for closing and opening the electric circuit while the other plates are mounted stationary and connected in series to the pilot The adsorbent plate 20 of the upper compart-4 ment 4 never requires to be reconditioned in ordinary service since any volatile substance bei'cles water which may condense on its surface will Llways be expelled from the plate during its retctivation in the desorbing phase. This is borne )ut from trials with a model of the non-autonatic type extending over several years when the )lates had lost none of their initial drying power md capacity.

To be suitable for use in the present drying ipparatus, the adsorbent plate must be highly aorous in texture so as to enable the water vapor :o readily penetrate to the interior of the plate. [t also must be mechanically strong and durable and not develop cracks duringthe rapid removal if the water vapor in the heating operation. The articles composing the platev must be rmly aonded together to prevent any loss of material in continued operation and to make it possible ;o use the plate without any protective covering. Finally the plate should have a high capacity as well as a high intensity for adsorbing water vapor. These various requirements are fullled by molding the plate Vfrom a three-component mixture comprising a desiccating agent, a fibrous filler and a binding agent. In order to be Aable to use a larger proportion of the desiccating agent in the mixture than has been possible by using gypsum as a binding agent according to U. S. Patent 2,067,920, further experimentation led to the discovery that the mineral bentonite was extraordinarily suitable as a binding agent. Not only was it found possible to use this binder in appreciably smaller quantity, but its use in the composition greatlyv facilitated the kneading and molding of the moist mixture into a homogeneous, plastic mass from which surplus water could be easily removed by compression in a specially designedv mold between liners of cloth or the like, and applying' the pressure gradually with increased force. The good plasticity of the mass also made it possible to impress in it without any effort a previously wound and evenlyspaced resistance wire coil into one half of the plate before adding theremainder of the mass in such a manner as to preclude formation of air pockets and nally expressing the surplus water from the composite slab in the mold. On

a manufacturing scale it would probably be most advantageous to produce the plates in halfthicknesses by extrusion. No claim is made, however, for any particular method in producing the molded plates with embedded resistance wires.

For experimental purposes plates of corrugated cross-section were made with the over-all dimensions 6 x 3 x 1". the thinnest part of the plate between the urrows being 1/2. They contained embedded Nichrome resistance wire coils wound on a 332" mandril, 16 ft. of 30 B. & S. ga. Chromel A wire being used for operating on 110 volt. Satisfactoryplates could be made rom commercial silica gel as well as Activated Alumina. Typical -mixtures were as follows:

genized by passing through a shredder. In both compositions the asbestos used Was a good grade of chrysolyte, size 5M20..

The field of application for the drying apparatus determines the choice of the desiccating agent to.be used. Generally silica gel has a broader range of adsorptivity, but a smaller dry'- ing intensity than Activated Alumina. The latter also has theadvantage of being effective at somewhat higher temperature, as for example in tropical countries. In certain applications where a particularly intense drying or desiccating action is required the use of soluble anhydride also comes into consideration, notwithstanding its comparatively high specific gravity and narrow range of effectiveness. In this case the drying action is due to a chemical binding of the water to form the hemi-hydrate of calcium. sulfate, whereas in the case of the desiccants mentioned previously the water is held by capillary condensationin the'pores of these substances What is claimed as new and useful is:

1. A drying'apparatus comprising the combination of a drying chamber adapted to receive materials to be dried and an adsorbing chamber, said chambers having a common wall,.a movable door in the wall, a moisture adsorbing unit'and a. heating element therefor within the adsorbing chamber, means for movably supporting said adsorbing unit, and means actuated by said supporting means when a predetermined weight of moisture has been adsorbed by said unit to energize said heating element, a second door separating the adsorbing chamber from the outer atmosphere to permit vapors liberated from the adsorbing unit, upon application ofheat thereto to escape into the outer atmosphere, thermostatic means to open said second door and `simultaneously effect the closing of the door between the chambers, said thermostatic means being heated simultaneously with the energizing of the heating element, and means for de-energizing said heating element when a desired weight of water has been removed from the adsorbing unit.

2. A drying apparatus comprising the combination of a drying chamber adapted to receive materials to be dried and an adsorbing chamber, A

said chambers having a common wall, a. movable door in the wall, a moisture adsorbing unit within the adsorbing chamber comprising a plurality of spaced moisture-adsorbing plates having electrical resistance wires forming heating means embedded therein, means for movably supporting said adsorbing unit, and means actuated by said supporting means when a predetermined weight of moisture has been adsorbed by said unit to energize said resistance wires, a second door separating the adsorbing chamber from the outer Parts (A) Silica gel-- 57 Asbestos 29 Bentonite 14 (B) Activated Alumina 'l0 Asbestos 20 Bentonite l 10 atmosphere, located approximately over the adsorbing unit whereby vapors liberated from the adsorbing unit, upon application of 4heat thereto, esscape by convection into the outer atmosphere, thermostatic means to open said second door and simultaneously effect the closing of the door between the chambers, said thermostatic means comprising a bimetallic strip having an independent heating element in association therewith and being energized simultaneously with the' energizing of the resistance wires of the adsorbing unit and means for de-energizing said resistance w-ires when a desired weight of water has been removed from the adsorbing unit.

3. A drying apparatus comprising the combination of a. drying chamber, adapted to receive materials to be dried, an adsorbing chamber in close proximity thereto and in communication therewith, a movable door between the said'chambers, a -movably supported moisture-adsorbing -from moisture yet allow said unit to move downa second door separating the adsorbing chamber from the outer atmosphere whereby the vapors liberated from the adsorbing unit, on application of heat thereto, can escape into the outer atmosphere by convection, said door-operative means comprising a bimetallic strip having independent heating means energized simultaneously with the heating means for the heating means of said adsorbing unit and means to .de-energize both heating means when a desired amountrof water has been removed from said adsorbing unit.

4. A drying apparatus comprising the combina- 10 tion of a drying chamber to receive materials to be dried, an adsorbing chamber in close proximity thereto, a moisture adsorbing unit in'said adsorbing chamber with heating means, a, movable door between the drying chamber and the adlsorbing chamber, a second door separating the adsorbing chamber from the outer atmosphere, means adapted to instantaneously close the said first door upon the incipient opening of the second door thereby permitting vapors liberated from the adsorbing unit to escape into the outer atmosphere, said second door being interconnected with the first door through the. instrumentality of a link supporting a pawl provided with a finger adapted to release a latch attached to the rst door from the said pawl engaging it when the finger of said pawl is seized during its downward travel by a. swinging hook pivoted on the side of the adsorbing chamber, a, bi-metallic strip having an independent heating element in association therewith, being energized simultaneously with the energizing of the heating means for said .adsorbing unit, a link connecting thek bimetallic strip and said second door whereby said door is Lopened when the bimetallic strip is bent upon being heated and means for de-energizing said heating means when a desired amount of moisture has been removed from said moisture adsorbing unit.

RALPH V. HEUSER. 

